Conventionally, there has been proposed an illumination device that turns on a light emitting diode (LED) when detecting a person with the use of a motion sensor.
For example, in an illumination device described in Patent Literature 1, a microcomputer unit (hereinafter, referred to “control circuit”) performs control to turn on and off a light-emitting unit composed of a plurality of LEDs connected in series to one another according to the output voltage of a motion sensor.
Such an illumination device requires to supply power to the control circuit, in addition to the LED, so as to drive them. Here, voltage required to drive the control circuit (hereinafter, such voltage is referred to as “driving voltage”) is lower than the voltage supplied from an external power source to turn on the light-emitting unit, and the illumination device described in Patent Literature 1 therefore reduces the voltage from the external power source with the use of a dedicated voltage-down circuit and supplies the control circuit with the reduced voltage.